Each hunter pet family belongs to one of three specific family roles: Cunning, Ferocity, or Tenacity. These determine which functional roles your pet is best at (tanking, damage, flexibility, and PvP), and specifies which talent tree it uses. See our home page for a list of families and the roles to which each belongs.
"Cunning pets, like spiders, have a mix of offensive and defensive abilities and are particularly useful in Battlegrounds and Arenas."
Cunning pets are the most flexible of the three talent trees. Their talents focus on utility and mobility, which makes them especially valuable in PvP fights. But that same flexibility also makes Cunning pets a good all-around choice for soloing and small groups.
"Ferocious pets, like cats, can dish out damage but can't take it as well."
Ferocity pets are all about the damage. Their talents focus on increasing both their damage and yours, and they have some nice abilities aimed at keeping them alive as well. Ferocity pets are popular in groups and raids, but can also help polish off enemies extra fast in solo play and PvP.
"Tenacious pets, like turtles, are more defensive and can occupy an enemy's attention while you stay at range."
Tenacity pets have a variety of talents for staying alive, protecting their friends, and keeping the enemy focused on them and not you. Tenacity pets are excellent for solo questing and leveling and can even tank for a small group in many situations.